Transistorized ignition system



1965 B. H. SHORT TRANSISTORIZED IGNITION SYSTEM Filed June 25. 1960 INVENTOR.

Brooks H. Shari ONQ- I His Afforney United States Patent 3,218,513 'I'RANSISTORIZED IGNITION SYSTEM Brooks H. Short, Anderson, Ind., assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Filed June 23, 1960, Ser. No. 38,205 12 Claims. (Cl. 315-219) This invention relates to an ignition system for an internal combustion engine and more particularly to an ignition system wherein a transistor controls the charging and discharging of an ignition transformer. This application is a continuation-in-part of application Serial No. 579,332 filed on April 19, 1956, and assigned to the assignee of this application and now abandoned.

In the present-day ignition systems, the current to the primary winding of the ignition coil passes through a set of mechanically actuated breaker points from a source of DC. current and voltage, such as a storage battery. The ignition coils used in these systems are a type of pulse transformer and have a primary and secondary coil winding. The flow of current in the primary coil winding will cause energy to be stored in the magnetic system of the coil. It has been found that this stored energy is equal to joules where L is the primary inductance of the coil in henries and i is the current in the primary coil winding in amperes.

When the breaker points of the system separate, this stored energy is quickly released from the magnetic system and charges the capacities of the primary and the secondary systems. The proportion of energy going to each system is determined by the relative capacities and inductances of each.

It is generally known, the value of the primary current when the contact points open deceases with engine speed as can be determined by the relation where E is the source voltage, R is the total resistance of the primary circuit, L is the primary inductance in henries and e=2.718. At low speeds the quantity an increase in either L or i will result in an increase in the energy stored in the primary winding. An increase in L, however, will result in a decrease in current in the primary circuit at high speed. The current in the present-day ignition systems heretofore has been limited to a value that can be carried by the breaker points without deterioration when the engine is at low speeds. This current is limited to a maximum of about 4 /2 amperes as it has been found that currents higher than this value would result in breaker point failures.

When the circuit according to the present invention is ice employed, the current to the primary coil winding may reach the value of 8 to 10 amperes without damage to the components of the system. In fact, the breaker points of the system of my invention will have almost an indefinite life because of the small currents which will pass therethrough. Further it is apparent that when a current of this magnitude is employed, the inductance of the primary circuit can be reduced to a much lower value than is used in the present-day systems. This, of course, will improve the current at the break at high speeds.

It is also known that the coils output wave front shape is dependent to an extent on the total inductance and capacitance of the primary circuit, and that the wave front becomes steeper as the total inductance or total capacitance of the primary circuit is reduced. A steep output wave front means that less time will be required to raise the secondary voltage to plug firing potential. Because of the short time, any energy loss due to fouled plugs is radically reduced, leaving the greater portion of the available energy for raising the plug to firing potential. This means that fouled spark plugs may be more readily fired.

The above advantages are achieved by controlling the current flow in the primary winding of an ignition coil by a transistor to provide a simple trouble-free ignition system which will be reliable in its operation. The tran sistor, when used in the ignition system, possesses further advantages over devices heretofore used as it conducts at the voltage output of the storage battery and does not require a warm-up time. This latter characteristic of a transistor will make ignition available at the very instant the ignition key is turned on.

It is therefore an object of the present invention to control the current flow in an ignition coil with a transistor, the conduction of which is controlled by a set of mechanically actuated breaker points.

A further object of the present invention is to use a transistor to control the circuit to the primary winding of an ignition transformer.

Another object of the present invention is to control the current flow from the battery to the primary windings of an ignition coil by a transistor that has its collector and emitter directly connected in circuit with the battery and coil winding and its base in circuit with a pair of timer points which are mechanically actuated.

Still another object of this invention is to provide an ignition system for controlling the firing of a spark plug of an internal combustion engine wherein a semiconductor such as a transistor is connected with a power source and primary winding of an ignition coil for controlling the current flow in the primary winding, and wherein the bias voltage applied to the semiconductor is applied thereto from a circuit network including a pair of breaker contacts and a voltage dividing network.

A further object of this invention is to provide a transistor ignition system employing transistors of the NPN type.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a schematic diagram of an ignition system made in accordance with this invention employing a PNP type transistor.

FIGURE 2 is a schematic illustration of an ignition system made in accordance with this invention employing an NPN type of transistor.

FIGURE 3 is a schematic illustration of a modified ignition system made in accordance with this invention employing an NPN type of transistor.

In FIGURE 1, the numeral designates a storage battery which acts as a source of current for an ignition system for an internal combustion engine. The battery may be of the standard 6 or 12 volts as used in presentday automobiles and has its output terminals connected to the leads 22 and 24. The ignition switch 26 is used to make and break the circuit to the ignition system as will be hereinafter described.

The transistor 28 shown is of the well-known PNP type having .a base b, a collector c and an emitter e. The PNP transistor as used in the circuit shown is characterized by the fact that current in the order of 8 to 10 amperes will flow from the emitter e to the collector c Whenever the base b is sufficiently negative with respect to the emitter e and the emitter e is sufficiently positive with respect to the collector c. The transistor 28 further will not at any time pass current from the emitter to the collector when the voltage in either direction approaches the voltage rating of the transistor if the base is not supplied with current. Another characteristic of the transistor shown is that the current flow between the emitter and collector is proportional to the flow of current between the emitter and base which, in turn, is proportional to the voltage diiference between the emitter and base.

The emitter e of transistor 28 is connected to positive lead 22. The collector c of the transistor 28 is connected through a junction 30 and the primary coil winding 32 to the negative lead 24. The secondary coil winding 34 supplies the ignition current and power through a distributor 35 to the spark plugs diagrammatically shown as 36. The coil winding 34 has one end connected to the grounded side of the primary coil winding 32 and the other end connected through the distributor 35 to the spark plugs 36 in the conventional manner.

The base b of transistor 28 is connected by a lead 37 through the breaker points 38 to the tap 40 on the resistance 42. The resistance 42 is connected across leads 22 and 24, and a resistance 44 is connected across leads 22 and 37. The condenser 46 which is connected between lead 22 and junction 30 minimizes voltage surges across the emitter and collector of transistor 28, and partially controls the wave front. The resistance 42 is preferably selected so only a small current flow will pass through to reduce the drain on the storage battery to a minimum. When the ignition switch 26 is initially closed the circuit shown will be immediately energized. When the points 38 are open the base b of transistor 28 will he at the same potential as the emitter e because of the resistance 44. The flow of current through resistance 42 will cause tap 40 to be negative relative to lead 22. transistor will become negative relative to the emitter e. When base b is negative, the transistor 28 will immediately conduct and pass current to the primary coil winding to build up magnet flux therein. This flux is stored in the ignition coil and represents the energy which is stored in the coil.

When the breaker points 38 open, the emitter-to-base circuit of transistor 28 is broken and the transistor 28 immediately stops conducting current. In this connection as the collector current in a transistor is much greater than the base current only a small current will be flowing through the points 38 at the instant they open. This will assure practically an indefinite point life. When the current through the collector ceases, the stored energy in the ignition coil will be released to cause the spark plugs to ignite as is well known to those skilled in the art.

Referring now more particularly to FIGURE 2 a transistor ignition system is illustrated which employs a transistor of the NPN type. In the system of FIG- URE 2, the-reference numeral 50 designates a source of direct-current power such as a storage battery which, as can be seen, is connected with an ignition switch 52. One side of the ignition switch 52 is connected with the junction 54 which is, in turn, connected with lead wires 56 and 58. The lead wire 58 is connected to a Thus when points 38 close, the base b of the shiftable breaker lever 60 having a breaker contact 62 which cooperates with a fixed breaker contact 64. The breaker arm 60 is operated by the usual cam member 66, it being understood that the cam member 66 is driven in synchronism with the engine to cause an opening and closing of breaker contacts 62 and 64.

The breaker contact 64 is connected to one side of a resistor 67, the opposite side of the resistor being connected with junction 68. The junction 68 is connected to one side of resistor 70, the opposite side of this resistor being connected directly to ground, as shown.

The reference numeral 72 in FIGURE 2 designates an NPN type of power transistor having an emitter electrode 74, a base electrode 76 and a collector electrode 78. It can be seen that the base electrode 76 of transistor 72 is connected with the junction 68, whereas the emitter electrode 74 is connected directly to ground. The collector electrode 78 of transistor 72 is connected to one side of the primary winding 80 of an ignition coil 82. The opposite side of the primary winding 80 is connected with a current limiting resistor 84 which is also connected with the lead wire 56.

The secondary winding of ignition transformer 82 has one side thereof connected directly to ground and has an opposite side thereof connected to one side of a spark plug 86. The opposite side of the spark plug 86 is connected directly to ground, as shown.

When the ignition switch 52 is closed it will be apparent that the ignition system will be energized from the battery 50. As the breaker cam 66 now rotates to open and close the breaker contacts 62 and 64, spark impulses will be applied to the spark plug 86 to cause a firing of the combustible mixture in the internal combustion engine and to therefore cause a starting of the engine. When the breaker contacts 62 and 64 are closed, it is apparent that the voltage dividing network consisting of resistors 67 and 70 is connected directly across the battery and that the junction point 68 will therefore be at some potential that is positive with respect to ground. It can be seen that when the junction 68 is at some potential positive with respect to ground a current will flow in the base and emitter circuit of transistor 72. When a current flows in the base and emitter circuit of transistor 72, a larger current will then flow in the collector and emitter circuit of transistor 72 to render it substantially fully conductive so that current will now be supplied from battery 50 to the ignition coil 80 through resistor 84 and through the transistor 72 to ground.

When the breaker points 62 and 64 open, the junction 68 is no longer connected to one side of the battery and it therefore can be seen that the base and emitter electrodes of transistor 72 will be at substantially the same potential to cut off the current flow through the collector and emitter circuit of transistor 72. It thus is seen that as the breaker contacts 62 and 64 open, the transistor 72 is rendered substantially fully nonconductive to prevent further current flow through the primary winding 80 of the ignition coil. This will, of course, cause a large voltage to be induced in the secondary winding 85 which is applied across the spark gap of spark plug 86 and therefore causes a firing of this spark plug and ignition of the combustible mixture of the engine. It will be apparent from the foregoing that with the system of FIGURE 2 ignition occurs at the opening of the breaker contacts 62 and 64.

Referring now more particularly to FIGURE 3, a modified ignition system is illustrated employing an NPN type of transistor wherein ignition occurs upon the closure of a pair of breaker contacts. In the system of FIGURE 3, the reference numeral 90 designates the source of direct-current power such as a storage battery, whereas reference numeral 92 designates an ignition switch. One side of the ignition switch is connected with junction 94 and a voltage dividing network consisting of resistors 96 and 98 is connected between junction 94 and ground.

The breaker contacts in FIGURE 3 are designated by reference numerals 100 and 102, the contact 100 being carried by breaker lever 104 which is operated by the breaker cam 107. The breaker lever 104 is connected with the junction point 106 of resistors 96 and 98, whereas the breaker contact 102 is connected directly to ground, as shown.

The system of FIGURE 3 employs an NPN transistor 110 having an emitter electrode 112, a base electrode 114 and a collector electrode 116. It is seen that the base electrode 114 of transistor 110 is connected with junction 106 via the lead wire 118.

The collector electrode 116 of transistor 110 is connected with the primary winding 120 of an ignition coil 122. The opposite side of primary winding 120 is connected to one side of the current limiting resistor 124 and the opposite side of this resistor is connected with junction 94. The secondary winding 126 of ignition transformer 122 has one side thereof connected directly to ground and has an opposite side connected with the spark gap of a spark plug 128. The opposite side of the spark plug 128 is connected directly to ground as is clearly apparent from FIGURE 3.

In FIGURE 3 when the ignition switch 92 is closed and when the breaker points 100 and 102 are closed, it can be seen that the junction 106 is connected directly to ground through the breaker contacts. Since the junction 106 is connected directly with the base electrode of transistor 110 and since the emitter electrode 112 of this transistor is connected directly to ground, it will be apparent that when the breaker contacts 100 and 102 are closed the emitter and base electrodes are at substantially the same electrical potential so that no current flow will exist in the base and emitter circuit. As a consequence of this, no current will flow through the collector and emitter circuit of transistor 110 and there therefore will be no current flow through the primary winding of ignition coil 120.

When the breaker points 100 and 102 open, the junction 106 is no longer connected directly to ground and the base electrode of transistor 110 will be at the same electrical potential as the junction 106. The electrical potential of junction 106 will be at some value positive with respect to ground, with the breaker contacts 100 and 102 in an open position, and it is therefore apparent that current fiow will occur in the base and emitter circuit of transistor 110. As a consequence of this base and emitter current in transistor 110, there will be a large collector and emitter current which will cause the transistor 110 to be substantially fully conductive and therefore cause a relatively large current flow through the primary winding 120 of the ignition coil. When the breaker point contacts close once more, the transistor 110 will be rendered nonconductive as described above to cut oif the current flow through primary winding 120 and therefore cause a spark at spark plug 128 due to the large voltage induced in the secondary winding 126 of the ignition transformer 122. It is apparent that in the FIGURE 3 embodiment of this invention ignition occurs upon the closure of the breaker contacts 100 and 102, rather than upon the opening of the breaker contacts as is the case in the embodiments of FIGURES 1 and 2.

While the embodiments of the present invention as herein disclosed constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An internal combustion engine ignition system for firing a spark plug of the engine comprising, a source of power, an ignition coil having a primary winding and a secondary winding, means connecting the secondary winding of said ignition coil with said spark plug, a threeterminal semiconductor means including a pair of currentcarrying terminals and a control terminal, means for connecting the current-carrying terminals of said semiconductor means in series with said power source and primary Winding of said ignition coil whereby the current flow through said primary winding is controlled as a function of conductance of said semiconductor means, means providing a reference potential point including voltage divider means connected across said power source, means connecting said control terminal with said reference potential point and means for varying the potential of said reference potential point in synchronism with operation of said engine.

2. An internal combustion engine ignition system for firing a spark plug of the engine comprising, a source of direct-current power, an ignition coil having a primary winding and a secondary winding, means connecting said secondary winding with said spark plug, an NPN type of transistor having a collector electrode, a base electrode and an emitter electrode, means connecting said power source, the primary winding of said ignition coil and the collector-emitter circuit of said transistor in series whereby the current flow through the primary winding of said ignition coil is controlled by said transistor, breaker contact means opened and closed in synchronism with operation of said engine, means connected across said source of direct-current power providing a reference potential point, means permanently connecting the base electrode of said transistor with said reference potential point, and means including said breaker contact means for varying the potential of said reference potential point in synchronism with operation of said engine.

3. An ignition system for an internal combustion engine comprising, a storage battery, a transistor including emitter, base, and collector electrodes, an ignition coil having a primary winding, means connecting said emitter electrode to one side of said storage battery, means connecting said collector electrode to one side of said primary winding, means connecting the opposite side of said primary winding to the opposite side of said storage battery, a pair of breaker contacts forming part of a circuit for applying at least a part of the total voltage of said storage battery across the emitter and base electrodes of said transistor of such a polarity as to render said emitter electrode positive with respect to said base electrode to thereby render said transistor conductive between said emitter and collector electrodes when said breaker contacts are closed, and a resistor connected between one side of said storage battery and one side of said breaker contacts and also connecting the emitter and base electrodes of said transistor to substantially equalize their potential when the breaker contacts are open.

4. An ignition system for an internal combustion engine comprising, a direct-current voltage source, first conductor means connected with one side of said direct-current voltage source, second conductor means connected with an opposite side of said direct-current voltage source, a transistor having emitter, base and collector electrodes, an ignition coil having a primary winding, a biasing resistor connected across said first and second conductor means, a tap located intermediate the ends of said resistor, means connecting said emitter to said first conductor means, means connecting said collector to one side of said primary winding, means connecting the opposite side and said primary winding to said second conductor means, a base circuit for said transistor including a pair of breaker contacts connected between the base electrode of said transistor and said resistor tap and further including a second resistor connecting the base electrode of said transistor and said first conductor means, whereby said transistor is rendered conductive to pass current to said primary winding when said breaker contacts are closed and is rendered nonconductive to block current flow to said primary winding When said breaker contacts are open, said second resistor substantially equalizing the potential of said emitter and base electrodes when said breaker contacts open.

5. An ignition system for an internal combustion en gine comprising, a source of direct current power, an ignition coil having a primary winding and a secondary winding, a transistor having emitter, collector and base electrodes, a main circuit connected across said source of power comprising in a series connection the emitter and collector electrodes of said transistor and the primary winding of said ignition coil, a second circuit in which are permanently interconnected the emitter and base electrodes of said transistor including a resistor, and means connected with the base electrode of said transistor for controlling the conductivity of said transistor in its emittercollector circuit in synchronism With operation of said engine.

6. An ignition system for an internal combustion engine comprising, a source of direct current power, a transistor having emitter, base and collector electrodes, an ignition coil having a primary winding and a secondary winding, means connecting the emitter-collector circuit of said transistor in series With the primary winding of said ignition coil and across said source of direct current power, voltage divider means having tap point connected across said source of direct current power, breaker contacts connected between the base electrode of said transistor and the tap point on said voltage divider, and means permanently connecting the emitter and base electrodes of said transistor.

7. An ignition control unit adapted to be connected with an ignition coil, distributor breaker contacts and a source of direct current comprising, a first conductive means which is adapted to be connected to one side of a pair of distributor breaker contacts, a second conductive means which is adapted to be connected to one side of a source of direct current, a third conductive means adapted to be connected with one side of the primary winding of an ignition coil, a transistor having emitter, collector and base electrodes, means connecting said emitter electrode of said transistor with said second conductive means, means connecting the collector electrode of said transistor with said third conductive means, means connecting the base electrode of said transistor with said first conductive means, and a circuit having electrical resistance connecting said first and second conductive means, said last named circuit having no intervening potential source and excluding said primary winding when said third conductive means is connected with one side of said primary winding, the opposite side of said primary winding and the opposite side of said breaker contacts being adapted to be connected with an opposite side of said source of direct current.

8. An ignition system for an internal combustion engine, comprising, terminal means adapted to be connected across a source of direct current, a three terminal semiconductor control device having a pair of current carrying terminals and a control terminal, an ignition coil having a primary winding and a secondary winding, a first circuit connected across said terminal means including the current carrying terminals of said semiconductor control device and the primary winding of said ignition coil, a second circuit connected across said terminal means in parallel with said first circuit, said second circuit being continuously energized when said terminal means is connected across said source of direct current, means connecting the control terminal of said semiconductor control device with a point on said second circuit, and means for varying the potential of said point on said second circuit in synchronism with operation of said engine.

9. An ignition system for an internal combustion engine comprising, a source of direct current, an ignition coil having a primary winding and a secondary winding, a three terminal semiconductor control device having a pair of current carrying terminals and a control terminal, a first circuit connected across said source of direct current including the primary winding of said ignition coil and the current carrying terminals of said three terminal semiconductor control device, a pair of breaker contacts, a second circuit connected across said source of direct current in parallel with said first circuit including said breaker contacts, and conductor means connecting a point on said second circuit with said control terminal of said three terminal semiconductor control device, said breaker contacts being connected between said point of said second circuit and the side of said source of direct current that is connected with one side of said primary Winding, said second circuit applying a forward bias to said semiconductor control device to bias it to a state of conduction when said breaker contacts are closed.

10. An ignition system for an internal combustion engine comprising, terminal means connectible with a source of direct current, an ignition coil having a primary winding and a secondary winding, breaker contacts, a three terminal semiconductor contact device having a pair of current carrying terminals and a control terminal, a first circuit connected across said terminal means including the current carrying terminals of said control device and said primary winding of said ignition coil, a first loop circuit connecting said control terminal and one of the current carrying terminals of said control device including said breaker contacts and a second loop circuit excluding said breaker contacts connecting said control terminal and the other current carrying terminal of said control device, said loop circuits excluding said source of direct current.

11. An electrical system comprising, a source of power, a current consuming device, a transistor having emitter, collector and base electrodes, a main circuit connected across said source of power comprising in a series connection said current consuming device and the emitter and collector electrodes of said transistor, a second circuit having no intervening potential source and excluding said current consuming device permanently connecting the emitter and base electrodes of said transistor, said second circuit including a circuit element having electrical resistance, and electrical switch contacts, the emitter base circuit of said transistor and said circuit element being connected across said source of power through said switch contacts whereby said switch contacts control the conductivity of said transistor in its emitter-collector circuit.

12. An ignition system for an internal combustion engine comprising, a source of power, an ignition coil having a primary winding and a secondary winding, a transistor having emitter, collector and base electrodes, a main circuit connected across said source of power comprising in a series connection the emitter and collector electrodes of said transistor and the primary winding of said ignition coil, a second circuit having no intervening potential source and excluding said primary winding permanently connecting the emitter and base electrodes of said transistor, said second circuit including a circuit element having electrical resistance, and distributor breaker contacts operated in synchronism with said engine, the emitter-base circuit of said transistor and said circuit element being connected across said source of power through said breaker contacts whereby said breaker contacts control the conductivity of said transistor in its emitter-collector circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,728,857 12/1955 Sziklai 307-885 2,878,298 3/ 1959 Giacoletto 315200.1 2,966,615 12/1960 Meyer et al. 315209 2,984,778 5/1961 Race 315-209 FOREIGN PATENTS 1,137,949 1/1957 France.

GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, JOHN W. HUCKERT, Examiners. 

2. AN INTERNAL COMBUSTION ENGINE IGNITION SYSTEM FOR FIRING A SPARK PLUG OF THE ENGINE COMPRISING, A SOURCE OF DIRECT-CURRENT POWER, A IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANS CONNECTING SAID SECONDARY WINDING WITH SAID SPARK PLUG, AN NPN TYPE OF TRANSISTOR HAVING A COLLECTOR ELECTRODE, A BASE ELECTRODE AND AN EMITTER ELECTRODE, MEANS CONNECTING SAID POWER SOURCE, THE PRIMARY WINDING OF SAID IGNITION COIL AND THE COLLECTOR-EMITTER CIRCUIT OF SAID TRANSISTOR IN SERIES WHEREBY THE CURRENT FLOW THROUGH THE PRIMARY WINDING OF SAID IGNITION COIL IS CONTROLLED BY SAID TRANSISTOR, BREAKER CONTACT MEANS OPENED AND CLOSED IN SYNCHRONISM WITH OP- 